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Homework Help: Energy and Power problem (change in tempurature)

  1. Jan 17, 2010 #1
    1. The problem statement, all variables and given/known data
    David is travelling in his car (1500 kg) at 72 km/h. He sees a dog on the road and hits the brakes, what is the final temperature of his brake pads if they have a combined mass of 10 kg, a heat capacity of 300 J/kgC and they start at 20 degrees Celsius?

    2. Relevant equations

    Change in T=T2-T1

    3. The attempt at a solution

    I am wondering if i have done this right

    = 1/2*1500kg*20m/s^2
    -3.0x10^5 J

    change in temperature =Q/mc
    =3.0x10^5 J/10 kg*300 J/kgC
    =100 degrees C
    100+20=120 degress Celsius

    120 is final temperature of break
    -Is this correct?
  2. jcsd
  3. Jan 17, 2010 #2


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    Science Advisor
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    Looks good! Some of the kinetic energy may be lost to sound, etc., but essentially, all of the kinetic energy is transformed to heat energy.
  4. Jan 17, 2010 #3
    Thank you!
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